For example, in a solar cell system, a solar cell module, which is a structure, is fixed and supported on a rack. This rack needs to be able not only to support the weight of the solar cell module, but also to withstand wind pressure exerted on the solar cell module, so it needs to have high strength. Since a solar cell module in the form of a flat panel is susceptible to high wind pressure, care has to be exercised in regard to the strength of the rack.
For instance, with the attachment structure of Patent Literature 1, support rails on which a combination of cylindrical bodies are provided, and the ends of a solar cell module are supported by these support rails. Because the cylindrical bodies themselves have large section modulus, a combination of cylindrical bodies gives the support rails high strength.
With the attachment structure of Patent Literature 2, a plurality of frames having a hat-shaped cross section are arranged in rows, and a solar cell module is fixed and supported on these frames. These hat-shaped frames also have large section modulus, so strength of the frames is high.